Absorption refrigeration system



N. E. HOPKINS July 16, 1968 ABSORPTION REFRIGERATION SYSTEM Filed Sept. 6, 1966 United States Patent Oflice 3,392,547 ABSORPTION REFRIGERATION SYSTEM Neil ELHOpkins, York, Pa., assignor to Borg-Warner Corporation, Chicago, Ill., a corporation of Illinois Filed Sept. 6, 1966, Ser. No. 577,322 5 Claims. (Cl. 62476) ABSTRACT OF THE DISCLOSURE An absorption refrigeration system using an ejector driven by relatively dilute absorbent solution tapped off ofthe line returning the dilute solution to the generator. Relatively concentrated solution is supplied to the suction side of the ejector for mixing with the dilute solution, and an additional line connects the absorber with the suction side of the ejector to assure sufficient head to avoid noisy operation.

This invention relates generally to absorption refrigeration apparatus and more particularly to an improved arrangement for circulating solution to the absorber.

A principal object of this invention is to provide an improved arrangement in absorption refrigeration apparatus by incorporating an ejector unit into the system so that a single solution pump is used in place of the two solution pumps normally used.

Another object is to incorporate into the system an ejector unit in association with the absorber in such a manner that the ejector unit will always have a sufiicient quantity of solution available to operate properly.

A further object is to incorporate into the system a recirculation line in association with the ejector to provide suflicient static head at the ejector suction to prevent noisy operation due to cavitation.

Other objects and advantages will be apparent from a reading of the following detailed description taken in conjunction with the drawing wherein:

The figure is a diagrammatic representation of an absorption refrigeration system embodying the principles of the present invention.

For the purpose of this specification, it will be assumed that the absorption refrigeration system described herein is of the type which employs a hygroscopic brine as the absorbent and water as the refrigerant. Inasmuch as lithium bromide solution has been found to be a suitable absorbing medium, reference will sometimes be made to the system employing this salt as the absorbent, but it should be understood that the invention has general application to absorption refrigeration systems using any of several other known absorbent-refrigerant combinations. Also for purposes of illustration, the concentrated solution means a solution of relatively higher concentration in lithium bromide (approximately 64.5 percent by weight at maximum capacity), While the dilute solution may be defined as a solution relatively lower in concentration of lithium bromide (approximately 59.5 percent by weight at maximum capacity).

Turning now to the figure, a first shell 10 is provided having a heat-exchanger 11 and a heat-exchanger 12 disposed therein. A pan or receptacle 13 positioned below heat-exchanger 12 combines therewith to form a condenser 14, and heat-exchanger 11 cooperates with the shell 10 to form a generator 15.

A second shell 16, ordinarily positioned below shell 10, includes a pair of heat-exhangers 17 and 18. Heatexchanger 17 is provided with a pin 19 which cooperates 3,392,547 Patented July 16, 1968 therewith to form an evaporator 20 and heat-exchanger 18 cooperates with the lower portion of shell 16 to provide an absorber 21. A pressure differential exists between shells 10 and 16 corresponding to the condenser pressure and evaporator pressure of the refrigerant (water).

Hot concentrated solution flows by gravity through line 22 from the lower portion of generator-condenser shell 10 to the heat-exchanger 23. In orderto increase the efiiciency of the system, it has been found desirable to provide a heat-exchanger 23 to transfer heat from the hot solution leaving the generator 15 to the relatively cool dilute solution from the absorber. A concentrated solution line 24 leads from the heat-exchanger 23 to another conduit running between a sump 26 connected to the bottom of shell 16 and an ejector unit as hereinafter more fully explained.

An ejector unit 27 is connected to the absorber and comprises an ejector inlet 28, ejector suction side 29 and ejector discharge 30. A line 31 connected to the ejector suction 29 is connected to or may form an extension of the concentrated solution line 24. The ejector 27 is also connected to absorber 21 through recirculation line 32 which may be an extension of line 31 or connected to line 31. The ejector 27 discharges through a conduit 33 to an absorber spray header 33a. The ejector inlet 28 is connected by conduit 34 to the discharge side of a generator pump 35.

The pump 35 draws cools, relatively dilute solution from the sump 26 of the absorber 21 through line 36 and discharges it through line 37 to generator 15. The discharge from pump 35 through line '37 passes through heat-exchanger 23 and is in heat exchange relation with the hot concentrated solution from generator 15.

Solution valve 49 throttles dilute solution flow to the gentrator in response to temperature control 52. Control 52 has its temperature sensitive element 53 in contact with concentrated solution flow from the generator. As the temperature of solution from the generator rises, corresponding to increased load, valve 49 opens to pass more dilute solution to the generator through line 37. correspondingly the flow of solution from the generator through line 22 is increased. By-pass line 50 around solution valve 49 permits a small amount of solution to flow to the generator when valve 49 is closed corresponding to low load operation. The amount of this minimum flow is determined by the sizing of orifices 51 in bypass line 50.

In the evaporator, water or some other suitable exchange medium is supplied to heat-exchanger 17, commonly referred to as the chilled water coil, through line 38 from the individual room air conditioning units (or some other load) and is returned to said units through line 39. The evaporator has a refrigerant pump 40 associated therewith, said pump being arranged to continuously circulate liquid refrigertant collecting in pan 19 to a spray header 41 above heat-exchanger 17. Under normal operating conditions, the chilled water from the room units, e.g., induction or fan coil units, enters the chilled water coil 17 at approximately 54 F. and leaves through line 36 at approximately 44 F.

Cooling water for the absorber and the condenser may be supplied from a cooling tower 42 of any conventional design, and is pumped by pump 52 through lines 43 and 44 to the heat-exchanger 18 disposed in the absorber section for removing heat generated by dilution of the concentrated absorber solution, and then through line 45 to heat-exchanger 12 disposed in the condenser section. Heat-exchanger 12 is connected by means of line 46 to a three-way valve 47 which is adapted to selectively divert water either through cooling tower 42 or a bypass line 48 arranged in parallel therewith. If the minimum cooling water temperature is called for, all of the water is diverted through the cooling tower, and if some higher cooling water temperature is desired, a portion or all of the water leaving the condenser heat-exchanger 12 through line 46 may be diverted to the bypass line 48 which is connected into line 44 downstream from the cooling tower.

The inventive feature herein relates to the ejector unit 27 and the manner in which it is connected into the refrigeration system. The ejection unit 27 makes possible the use of a single solution pump in place of the two solution pumps normally used. The use of two pumps is illustrated in US. Patent 3,254,499 on Absorption Refrigeration Apparatus and Method, issued on June 7, 1966 (referred to above). Hot concentrated solution flows from the generator 15 to the ejector 27 through line 22, the heat-exchanger 23, line 24 and line 31. Discharge from the pump 35 flows through line 34 and provides the motive force for ejector 27. It will be observed from the FIGURE that the ejector suction 29 is connected to two sources of fiuid. One is the hot concentrate line 24 and the other is the sump 26 to which the ejector 27 is connected through line 31 and line 32 referred to as the absorber recirculation line. By way of example, the ejector 27 may use as its motive fiuid about 45 gpm. of dilute solution coming from the solution pump discharge through line 34. At peak load, this is mixed with about 20 g.p.m. of concentrated solution from the generator 15 coming through line 24 to provide a mixture of about 65 g.p.m. of a solution of intermediate concentration which goes to the spray header 33a. The recirculation line 32 provides extra solution to the ejector suction 29 i.e., a quantity in addition to that provided by the hot concentrate line 24, so that the ejector 27 will never be starved for solution. This stabilizes the suction fiow to the ejector and the suction pressure will be maintained substantially constant. The ejector 27 is positioned below the shell 16 and close to the floor to provide a maximum static head at the ejector suction 29. Cavitation effects are also reduced by this arrangement. In addition, the substitution of an ejector for a pump unit is a large cost saving.

The important feature of this invention relates then to recirculation line 32, which makes available to the eductor suction line 31 additional solution above that available from line 24 in case the eductor tends to pump more solution than is available from line 24.

This feature is particularly important where the solution flow from line 24 is a variable, corresponding to the use of solution fiow control 49. While at peak load 20 g.p.m. of concentrated solution would normally be available from line 24 (in the previous example), at 20 percent load this flow would be approximately 4 g.p.m. With the eductor selected to handle 20 g.p.m. from line 31, this means that at 20 percent load 16 g.p.m. would flow from recirculation line 32. Without this recirculation line 32, at this condition, the solution level in line 31 would fall to the point where cavitation would take place, with accompanying noise.

In view of the fact that the generator 15 is located at a higher elevation than absorber sump 26, and also in view of the fact that the generator operates at an appreciably higher operating pressure than the absorber, flow from the generator into suction line 31 of the eductor is assured, as long as solution flow from the generator is available. Any tendency for recirculated flow from the absorber recirculation line 32 can only proceed after the available fiow from the generator has been taken care of. The liquid level in return line 22 will rise sufiiciently so that the pressure at point (a) in line 24 slightly exceeds the pressure (b) in line 32, in which case any flow made available from the generator flows to the eductor suction line 31, in

preference to any recirculation flow from recirculation line 32. Flow from recirculation line 32, therefore, only makes up the difference between the amount required to satisfy the eductor suction flow and that supplied by the generator from line 24. It should be mentioned that in case the quantity flowing from the generator should happen to exceed the suction capability of the eductor, the excess would simply flow through recirculation line 32 into the absorber sump. Aside from a certain inefiiciency in the operation of the plant, depending upon the quantity of such flow, this would cause no detriment to the operation of the system.

While the use of an ejector to send solution from a generator to an absorber spray header is shown in US. Patent 2,565,943 (Absorption Refrigeration System issued Aug. 28, 1951), that patent does not disclose or suggest the dual connection to the ejector suction which permits a greater amount of solution to go to the ejector than would otherwise be possible.

Thus it will be apparent that the present invention advantageously provides an improved absorption refrigeration system in which the necessity for one pump is eliminated. In its place, a simple, substantially maintenance free ejector is provided. Moreover, the ejector is so connected in the system that the output to the absorber is assured by connecting a recirculating line between the absorber and the ejector to maintain a relatively constant static head on the ejector suction. Maintaining this static head also reduces undesirable cavitation effects and concomitant noise.

While a preferred embodiment of th invention has been specifically disclosed, it is understood that the invention is not limited thereto as certain variations will be readily apparent to those skilled in the art and the invention is to be given its fullest possible interpretation within the terms of the following claims.

I claim:

1. The combination of absorption refrigeration apparatus including:

an evaporator, an absorber, a generator and a condenser connected to provide a closed refrigeration circuit;

first means for conducting a relatively dilute solution from said absorber to said generator;

a pump associated with said first means for withdrawing dilute solution from said absorber;

second means for conducting a relatively concentrated solution from said generator to said absorber;

an ejector associated with said second means to forward a solution to a spray header of said absorber; means connecting the discharge side of said pump to the inlet side of said ejector whereby discharge from said pump provides motive power for said ejector; means connecting the suction side of said ejector with said second conducting means; the improvement comprising means connecting the suction side of said ejector with said absorber.

2. The combination of claim 1 wherein said ejector is so positioned relative to said absorber that a maximum static head is maintained at the ejection suction.

3. The combination of claim 1 wherein said means connecting the suction side of said ejector with said absorber comprises a direct line connection between said absorber and said ejector.

4. The combination of claim 1 wherein said means connecting the suction side of said ejector with said absorber is constituted by piping which provides sufficient solution flow from the absorber to satisfy flow requirements at the suction port of said ejector under all operating conditions.

5. The combination of claim 1 wherein said absorption apparatus includes valve means for varying the fiow of concentrated solution from said 5 6 generator to said absorber whereby there is a reduc- 2,648,957 8/1953 Berestneff 62-489 tion in solution available from the generator at re- 2,722,806 11/1955 Leonard 62-489 duced loads. I 3,158,008 11/1964 Aronson 62483 References UNITED STATES PATENTS 5 3,279,206 10/1966 Leonard 62-141 2,565,943 8/1951 Berestnelf 62--141 LLOYD L. KING, Primary Examiner. 

